The present invention relates both to imaging plate scanning systems and to imaging plate erasing systems. In general, the present invention relates to all forms of medical imaging plates, however, a particular preferred application of the present invention is related to storage phosphor imaging plates.
Imaging plates, such as storage phosphor imaging plates, have become standard in the field of Computed Radiography (CR) as the medium onto which an image of a portion of the patient""s body can be stored. The image on such a phosphor imaging plate is extracted by scanning the imaging plate with a scanner. Typically, a phosphor imaging plate is scanned by passing a scanning laser beam over the surface of the imaging plate while recording light emitted from the imaging plate in response to the laser beam. By recording the emission corresponding to each of the pixels of the imaging plate with a detector such as a photomultiplier, the image stored therein can be re-created (such that it can be displayed on a computer terminal).
The act of scanning an imaging plate by passing a scanning laser beam thereacross is inherently destructive (i.e.: it releases the energy stored in the phosphor screen). As such, a particular image stored on an imaging plate can only be scanned (i.e. read) once. Although such scanning of the imaging plate releases the image, thereby erasing the image, such erasure is not complete and the imaging plate may still contain ghost images, lines or other image artifacts caused or not yet fully erased by the scanning procedure itself. Accordingly, it is necessary to completely and evenly erase an imaging plate before it can be re-used to store another image thereon.
To preserve a high image quality, phosphor imaging plates are typically housed within imaging plate cassettes to protect them from light, dust, fingerprints, and other image quality reducing artifacts. Such cassettes offer protection for the imaging plates, thus ensuring a long life such that the imaging plate can be reused again and again.
To reuse an imaging plate, it must first be scanned, and then erased. Both scanning and erasing release images on the imaging plate by exposing the imaging plate to roughly the same visible wavelength of light. It is, therefore, important to ensure that the imaging plate is not inadvertently exposed to such erasing wavelengths of light prior to scanning. Accordingly, scanning and erasing of the imaging plates are typically carried out in different machines, or at widely spaced apart locations within the same machine. When separate scanning and erasing machines are used, the imaging plate is typically hand transported therebetween while stored in the imaging plate cassette. Specifically, the phosphor imaging plates are first scanned in a scanner, and then are hand carried and placed into a separate erasing machine which passes the plate under a suitable wavelength of light such that all images stored therein are released.
Therefore, it is desirable to provide a combined imaging plate scanning and erasing system such that it is not necessary to remove an imaging plate from a cassette, scan it with a scanner, remove it from the scanner, place it back into the cassette, hand carry the cassette to an erasing machine, insert the imaging plate into the erasing machine, erase the imaging plate and then return the imaging plate to the cassette for future use.
Another problem common to both scanning and erasing machines is the manner in which the imaging plates are removed from the cassette. Sometimes, this is simply done by hand (with the imaging plates then placed by hand into the scanner or eraser). In addition, a variety of bulky systems using vacuum, gravity, or friction extraction motorized devices have been used to remove an imaging plate from a cassette. One problem with such systems are that they often tend to handle the imaging plate rather roughly. This is especially true of gravity systems in which the cassette is opened such that the imaging plate simply falls into a machine.
Therefore, it is desirable to provide a system which gently and automatically removes an imaging plate from a cassette prior to scanning and gently and automatically returns the imaging plate to the cassette after the imaging plate has been erased.
Yet another problem common to existing imaging plate scanners and to existing imaging plate erasing machines is that they tend to be very large. This is especially true in the case of large combined scanning and erasing systems due to the fact that large numbers of imaging plate and imaging plate cassette designs are already in circulation. Accordingly, manufacturers tend to design scanning and erasing machinery which is adapted to deal with these pre-existing plate and cassette designs, rather than simultaneously design imaging plates, cassettes, scanners and erasing systems which would together operate to provide more spatially integrated and efficient systems. Existing cassette designs, in particular, are often poorly suited to automation, necessitating large, bulky scanning and erasing systems which are not designed to handle these imaging plates (and their associated cassettes) within small spaces.
Moreover, in many of these large existing systems, it is typically necessary to position the scanning mechanism some distance from the erasing mechanism simply to prevent light from the erasing mechanism from entering the scanning mechanism. Being so large, these existing systems must unfortunately move the imaging plate through a considerable distance therein. Such long pathways of travel (which require many separate devices to move and position the imaging plate at various locations therein) have many drawbacks. For example, complex positioning systems which move imaging plates considerable distances frequently introduce positioning errors which can cause imaging problems, or simply cause the imaging plate to jam while moving through the system. Extracting a jammed imaging plate from a location deep within a scanner or erasing system can be frustrating and time consuming.
Therefore, it is especially desirable to provide a compact combined imaging plate scanning and erasing system which is much smaller than existing systems, moving its imaging plate a shorter distance Advantages of such a system would include its portability, space saving size, reduced system complexity, and increased ease and speed of operation.
The present invention provides a small, compact combination system for both scanning and then erasing an imaging plate. Although the present invention is ideally suited for use with storage phosphor imaging plates (also known as imaging xe2x80x9cscreensxe2x80x9d), it is not so limited.
The present system comprises a compact housing into which an imaging plate cassette is first inserted. An imaging plate infeed assembly within the housing is provided to pull the imaging plate cassette into the housing, open the imaging plate cassette (when it is positioned within the housing) and then remove the imaging plate from the imaging plate cassette for scanning followed by erasing.
In a preferred aspect, the present invention provides a combined imaging plate scanning and erasing system which comprises: (a) a housing; (b) an imaging plate infeed assembly positioned within the housing, the imaging plate cassette infeed assembly comprising: (i) a mechanism to pull an imaging plate cassette into the housing; (ii) a mechanism to open the imaging plate cassette; and (iii) a mechanism to remove an imaging plate from the cassette; (c) a scanner positioned within the housing; (d) a curved path erasing assembly positioned between the imaging plate infeed assembly and the scanner; and (e) an imaging plate transportation assembly to move the imaging plate back and forth in a path extending from the imaging plate cassette, past the erasing assembly and through a scan area adjacent to the scanner.
In preferred aspects, the entire body of the imaging plate cassette is pulled fully within the housing of the system prior to opening the cassette and removing the imaging plate positioned therein. An advantage of this preferred aspect of the invention is that the cassette is opened within the darkened interior of the housing, thereby avoiding exposing the imaging plate to any unwanted light which may degrade the image.
In preferred aspects, the imaging plate cassette infeed assembly comprises various components including an imaging plate infeed assembly which comprises: (a) a mechanism to pull an imaging plate cassette into the housing; (b) a mechanism to open the imaging plate cassette; and (c) a mechanism to remove an imaging plate from the cassette. After the imaging plate has been scanned and erased (as will be explained) these same mechanisms are operated in reverse order to place the imaging plate back into the cassette, close the cassette and then push the cassette out of the housing. As such, the present cassette xe2x80x9cinfeedxe2x80x9d assembly advantageously operates both as a cassette xe2x80x9cinfeedxe2x80x9d and a cassette xe2x80x9coutfeedxe2x80x9d assembly.
In preferred aspects, the imaging plate cassette is inserted through a slot in the side of the housing of the device such that a portion of the cassette is positioned within the housing. The cassette infeed assembly is then activated to pull the cassette into the housing. At the end of the scanning and erasing procedures, the cassette (with the imaging plate therein) is re-positioned with a portion sticking out of the slot such that an operator can simply grasp onto the cassette and then pull it fully out of the housing.
In preferred aspects, the mechanism which pulls the imaging plate cassette into the housing (and pushes it out after the imaging plate therein has been scanned and erased) comprises a movable shuttle which holds onto the imaging plate cassette; and a shuttle positioning assembly which moves the shuttle back and forth within the housing. Preferably, the shuttle moves a distance sufficient such that the entire body of the cassette can be pulled into the housing after the shuttle has gripped onto the cassette.
In optional preferred aspects, alignment guides and detent mechanisms are provided (either on one or both of the shuttle and the cassette) to ensure that the cassette is both firmly positioned on the shuttle and correctly centered on the shuttle. An advantage of centering the cassette on the shuttle is that different sized cassettes (each containing different standard or non-standard sized imaging plates) can be used by the present invention. In fact, with no modification being required to the present invention, it can sequentially accept, scan and erase different sized imaging plates (housed in different sized imaging plate cassettes). Furthermore, as will be seen, each of the present scanning and erasing assemblies, and the present imaging plate transportation systems are suited to move different sized imaging plates therethrough, without introducing positioning errors as the imaging plates are moved therethrough.
An imaging plate cassette is a generally flat, plate like structure. In preferred aspects, the scanner which is incorporated into the present system has a low vertical profile (i.e.: it""s short), and the imaging plates are slidably moved across the top of a reference plate which covers this scanner in a flat path which passes right on top of the scanner. Accordingly, in preferred aspects, the present invention provides a very compact design with the cassette and the scanner being positioned directly on top of one another. This can be accomplished either by positioning the cassette directly above (or directly below, or side by side) the scanner. In preferred aspects, the scanner used in the present invention is a circular rotating multi-head scanner, offering the advantages of fast scanning within a low vertical profile.
Having such a vertically compact design, the present invention further comprises novel systems for opening the cassette and for pulling the imaging plate out of the cassette, with these operations being performed in a minimal amount of vertical space. In various aspects, novel systems to unlatch (i.e. unlock) the cassette and to open its top cover just enough to pull the imaging plate out, are provided. In one preferred aspect, these systems comprise a claw which is dimensioned to latch onto the top cover of the cassette and pull the top cover open as the shuttle moves the cassette to a final position within the system housing. In one exemplary aspect, this claw is biased upwardly, and moves along a track.
The present invention further comprises a novel curved path erasing assembly which is advantageously positioned between the scanner and the cassette infeed mechanism. In preferred aspects, the erasing assembly comprises a curved structure which flips the imaging plate over as the imaging plate is removed from the cassette and is fed into the scanner.
In various aspects of the invention, the curved structure in the erasing assembly comprises either a curved window (along which the imaging plate slidably passes) or a curved window spaced apart from a curved element (with the imaging plate passing slidably therethrough). As such, the present invention provides a very compact erasing assembly. Being curved, the present erasing assembly considerably reduces the overall size of the present invention. Specifically, by flipping the imaging plate over as it passes therethrough, the present curved erasing assembly permits the infeed path of the cassette into the device to be generally parallel to the path the imaging plate takes across the scanner. Doubling the path through which the imaging plate travels over upon itself in this manner effectively cuts the overall length of the present system in half. Importantly, the present erasing assembly both erases an imaging plate, and guides the imaging plate through the system.
In various aspects, an erasing light source (or sources) may comprise a fluorescent light or a plurality of fluorescent lights or LEDs or a plurality of LED arrays positioned adjacent to (or spaced slightly away from) the curved window, passing erasing light through the curved window, toward the surface of the imaging plate. An advantage of such a curved window design is that the curvature of the window is used to change the direction of travel of the imaging plate while the window permits erasing light to pass therethrough. Specifically, the curved nature of the present erasing system specifically permits the imaging plate to be fed out of the erasing system in a path which is parallel to path in which the imaging plate was fed into the erasing system. Accordingly, a very compact erasing system design is achieved.
In preferred aspects, one or both of the curved window and the curved element positioned adjacent thereto have surfaces which are fabricated from a low friction material. Moreover, in such preferred aspects, various surfaces of the erasing assembly may be at least covered with highly reflective materials thus minimizes light leakage and thereby increases the overall effectiveness of the erasing procedure. Specifically, in these various preferred aspects, a highly reflective surface is disposed around the erasing light source to reflect erasing light through the curved window and onto the surface of the imaging plate sliding thereover.
An advantage of fabricating the curved window (and optional curved element positioned adjacent thereto) from low friction materials is that the imaging plate will slide easily theracross. Preferably, this results in the advantage that it is only necessary to provide a system to feed the imaging plate into one end of the erasing assembly (e.g.: a roller), and a system to extract the imaging plate from the other end of the erasing assembly (e.g.: another roller). As such, it is not necessary to provide a transportation mechanism within the erasing assembly itself to move the imaging plate therethrough.
An advantage of using either fluorescent tube lighting or LED erasing lights in the erasing assembly (especially when also using highly reflective coatings within the erasing assembly) is that the entire erasing assembly need only comprise a short structure relative to the overall length of the imaging plate passing therethrough. Stated another way, only a portion of the imaging plate need be disposed adjacent to the erasing assembly at any time. As such, a xe2x80x9cmiddle bandxe2x80x9d of the imaging plate can be passing through the erasing assembly at the same time that the proximal end distal ends of the imaging plate extend out of the erasing assembly. In contrast, many existing erasing systems are much larger and the entire imaging plate must be positioned within an erasing xe2x80x9cchamberxe2x80x9d such that the entire imaging plate is erased (by turning on erasing lights in the chamber) at the same time.
As such, it is not necessary for the present invention to provide a transportation mechanism within the erasing assembly itself, or to first position the entire imaging plate within the erasing section of the device and then later remove the imaging plate. Rather, in accordance with the present invention, movement of the imaging plate can be controlled without a transportation mechanism within the erasing assembly itself since at least one end of the imaging plate will protrude from the erasing assembly at all times. This protruding end or ends can easily be grabbed by a roller, etc. at either the infeed or the outfeed end of the erasing assembly.
In optional preferred aspects, the erasing light(s) of the present erasing system are positioned around the outer (convex) surface of the curved window. An advantage of erasing around the outer surface of the curved window (as compared to erasing around the inner surface of the curved window) is that the outer surface is longer than the inner surface, yielding a greater distance over which the erasing can be carried out. Also, more physical space is available for positioning multiple erasing light sources theraround.
An imaging plate transportation assembly is provided to move the imaging plate back and forth in a path extending from the imaging plate cassette, past the erasing assembly and past the scan area adjacent to the scanner. Specifically, and in accordance with the preferred method, the imaging plate is fed into the device until it reaches a position at which it is stopped, and its direction of travel is reversed, passing by the scanner and then through the erasing assembly. As such, the present method specifically provides that the imaging plate is first moved fully into the device, stopped, and then is sequentially scanned and erased while being withdrawn. It is be understood, however, that the present invention also encompasses those applications in which the imaging plate is scanned prior to its direction of travel being reversed (such that it is scanned while being inserted, stopped, and then erased while being withdrawn from the device).
In preferred aspects, the scanner comprises a multi-head scanner, and more preferably a rotating multi-head scanner, and most preferably a rotating three-head scanner. However, it is to be understood that the present scanning system is not so limited.
In one preferred aspect of the invention, the scanner is covered by a reference plate and the imaging plate is slid across the reference plate (passing through a scan area therealong). Preferably, the imaging plate is moved across the surface of this reference plate by a belt roller or other device which firmly positions the imaging plate against the reference plate. In preferred aspects, a center portion of the belt (between two rollers suspending the belt) is biased directly against the reference plate.
In preferred aspects the reference plate has a slot passing therethrough and the scanning head(s) of the scanner move along the slot such that light from the scanning head is directed across the imaging plate as the scanning head is moved along the slot. In most preferred aspects, a rotary scanner is used. Accordingly, in these preferred aspects, the slot in the reference plate is also curved.
An advantage of this system is that, by positioning the imaging plate firmly against the reference plate which covers the scanner, a very good light-tight seal is maintained at the scan area where the imaging plate is actually scanned. An important advantage of maintaining such a very good light-tight seal at this location is that it avoids the need for a light filter between the erasing and scanning portions of the present invention. Thus, the erasing assembly can be positioned very close to the scanning assembly.
A further advantage of the present novel system of slidably moving the imaging plate across a reference plate which covers the scanner is that the imaging plate is maintained at a known (small) distance from the scanning heads passing across thereunder. As this separation distance between the imaging plate and the scanning heads remains constant (both as the imaging plate is moved across the reference plate of the scanner and as the scanning heads are rotated such that a scanning beam passes across the surface of the imaging plate) it is possible to advantageously focus the laser beam from the scanning heads into a small spot on the imaging plate (thus achieving constant laser spot size on the imaging plate). This advantage is particularly beneficial when reading the image on the imaging plate as uneven spot size results in unwanted image artifacts on the final (on screen) image. A further benefit of the present preferred scanning system is that the angle of the scanning laser beams with respect to the imaging plate remains constant as the scanner""s scanning heads pass across the surface of the imaging plate.
In accordance with the present system, a preferred method of scanning and then erasing an imaging plate with a combined imaging plate scanning and erasing system is also provided. This method may preferably comprise: (a) inserting an imaging plate cassette into the combined imaging plate scanning and erasing system, wherein the imaging plate is stored within the imaging plate cassette; (b) pulling the imaging plate cassette into the combined imaging plate scanning and erasing system; (c) opening the imaging plate cassette; (d) removing the imaging plate from the imaging plate cassette; (e) moving the imaging plate in a path extending past a curved erasing assembly and then through a scan area adjacent to a scanner; (f) scanning an image on the imaging plate with the scanner; (g) moving the imaging plate back through the scan area and then back past the erasing assembly; (h) erasing the imaging plate with the erasing assembly; (i) placing the imaging plate back into the imaging plate cassette; (j) closing the imaging plate cassette; and (k) pushing the imaging plate cassette out of the combined imaging plate scanning and erasing system.
In preferred aspects, the imaging plate is removed from the cassette (preferably after at least a portion of the cassette has been pulled within the housing of the system). Thereafter, the imaging plate is first moved through the erasing assembly then passing at least partially across the scanner. (In particular, the imaging plate is preferably passed through a scan area adjacent to a reference plate which covers the scanner).
In most preferred aspects, the imaging plate is moved a distance such that its distal end passes fully across the scan area (and across the scanner) and is positioned in an outfeed area distal to the scanner. Thereafter, the imaging plate is moved in an opposite direction, moving back across the surface of the reference plate covering the scanner, passing through the scan area, at which time it is then scanned. After passing across the scanner, the imaging plate then passes back through the erasing assembly, at which time any residual images or image artifacts are erased by the erasing system (which is only then turned on).
In an additional erase only mode of operation, the present system can be used to erase imaging plates without first reading them. This is a standard recommended practice prior to exposing imaging plates when they have been sitting idle for an extended period. In such cases the plates can pick up noise artifacts due to background radiation including cosmic rays. In this mode, the erase lights can be illuminated continuously both during the in feed direction and the out feed direction of imaging plate motion. This has the benefit of slightly reducing the time required to complete an erase cycle.
In the preferred aspect of the invention in which a multiple-head rotary scanner is used (and in which successive scanning heads pass along a curved slot in a reference plate covering the scanner) the imaging plate is first advanced to a position such that its proximal edge passes fully past a curved slot in the reference plate. At this position, a distal portion of the imaging plate will be received within the outfeed area while a portion of the imaging plate remains positioned on top of the scanner. As will be explained, an advantage of this design is that the outfeed area need even not be as long as the imaging plate. In preferred aspects, the outfeed area is itself curved downwardly in front of the scanner, further saving space in the present design.
An advantage of using a single friction belt drive to slide the imaging plate over the surface of the reference plate covering the scanner is that this avoids image artifacts caused by speed variation and hand-off errors which may instead occur in the case of multiple driving elements.
A further advantage of the present curved path erasing system comprising a curved window spaced apart from a curved member is that each of these curved elements can be attached to separate components of the system such that when the present device is opened, these two portions of the eraser assembly move apart, permitting easy access to an image plate which has become jammed in between.
It is a further advantage of the present system that the scanner and the erasing assembly can be positioned close enough together such that portions of the imaging plate can be erased at the same time as other portions of the imaging plate are being scanned.
Being very compact, the present device is portable and may be moved room-to-room in a hospital or laboratory setting. In contrast, all known existing systems are large floor standing devices, typically the size of a large refrigerator.